net/packet: Remove unused macro BLOCK_PRIV

BLOCK_PRIV is never used after it was introduced.
So better to remove it.
Reported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: NWang Hai <wanghai38@huawei.com>
Acked-by: NWillem de Bruijn <willemb@google.com>
Signed-off-by: NJakub Kicinski <kuba@kernel.org>

net/packet/af_packet.c

@@ -177,7 +177,6 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
 #define BLOCK_LEN(x)		((x)->hdr.bh1.blk_len)
 #define BLOCK_SNUM(x)		((x)->hdr.bh1.seq_num)
 #define BLOCK_O2PRIV(x)	((x)->offset_to_priv)
-#define BLOCK_PRIV(x)		((void *)((char *)(x) + BLOCK_O2PRIV(x)))
 
 struct packet_sock;
 static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,